Electrolytic metal processing control circuit



United States Patent ()filice 3,336,214 ELECTROLYTIC METAL PROCESSING CONTROL CIRCUIT Z. Roman Cnota, P.O. Box 105, Pulaski, Wis. 54162 Filed July 7, 1964, Ser. No. 380,764 Claims. (Cl. 204228) ABSTRACT OF THE DISCLOSURE An electrolytic apparatus including a control circuit operating through the bath to prevent resetting of the apparatus to a subsequent operating cycle upon completion of the previous cycle until the article being processed is removed from the bath.

This invention relates to a control circuit for controlling electrolytic metal processing of a metal article immersed in an electrolytic bath.

In electrolytic metal processing, such as electroplating, electropolishing, anodizing, etc., it is sometimes desirable to control the duration of current flow between the electrodes, one of which constitutes the metal article to be processed or treated, and through the electrolyte in order to precisely control the amount or degree of electrolytic processing. Moreover, in many cases it is desirable that several such metal articles be separately processed one after the other in succession. This may be achieved, by means of presently available equipment, by the manual manipulation of certain adjustable controls or switches before each new metal article is treated. Such equipment, however, requires a relatively skilled operator and does not lend itself to the incorporation of automatic dipping apparatus which eifects immersing of the articles in the electrolyte one at a time in sequence.

The present invention, on the other hand, provides a control circuit which realizes completely automatic operation to the end that the operator only has to handle the separate articles to be processed and need not position any switches or controls in the time interval between the treatmentof one article and the processing of the next. In addition, without any change in the control circuit of the present invention, automatic dipping equipment may be employed to free the operator of the task of dipping each article in the electrolytic bath.

It is, therefore an object of the present invention to provide a new and improved control circuit for controlling electrolytic metal processing of a metal article immersed in an electrolytic bath.

A control circuit, constructed in accordance with one aspect of the invention, includes control means, operable responsive to immersing a metal article in an electrolytic bath, for translating direct current through the metal article and the bath to effect electrolytic processing of the article. Means are provided for automatically terminating the direct current upon the expiration of a predetermined time interval, thereby to terminate the electrolytic processing even though the article remains immersed in the bath. The control circuit also includes means for preventing a repeat operation of the control means until the metal article has been removed from the bath.

The featuresof this invention which are believed to be 3,336,214 Patented Aug. 15, 1967 new are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood, however, by reference to the following description in conjunction with the accompanying drawing which schematically illustrates an electrolytic metal processing (specifically electropolishing) control circuit constructed in accordance with the invention.

Turning now to the structural details of the drawing, block 10 depicts a source of conventional A.C. line volt-' age prevalent throughout the United States, namely a power supply for providing volts,'60 cycles per second, alternating current. One output terminal of AC. line voltage source 10 is grounded, while the other (namely, the high potential terminal) is connected to the movable contact 11 of a simple manually adjustable two-position, olfon switch 12. Fixed contact 13 of switch 12 is connected to one terminal of the primary winding 15 of a two-Winding transformer 16 and also to one terminal of the primary winding 17 of another two-winding transformer 18, the other terminals of windings 15 and 17 being connected to ground. The secondary winding 21 of transformer 16 is coupled to a conventional full-wave bridge rectifier 22 comprising four diode rectifying devices. When switch 12 is closed, the combination of transformer 16 and full-wave rectifier 22 convert the AC. line voltage to direct or unidirectional voltage which, of course, is capable of supplying direct current.

In the embodiment illustrated, the control circuit controls electropolishing of metal articles. It will become apparent, however, that the invention may be practiced in any electrolytic metal processing environment. Electropolishing, as is well known, removes metal from the surface of a metal article or its oxide film when direct current of sufiicient amplitude is translated through the electrolytic bath and the article. As shown in the drawing, a tank or container 24 contains an electrolyte or electrolytic bath 25. The metal article to be processed is dipped or immersed in the electrolyte and forms the anode electrode 26. The other or cathode electrode 27 is also immersed in the electrolytic bath. The combination of bath.

cathode electrode and the electrolyte. For example, if it is.

desired to polish stainless or high-chrome steel, the cathode is made of lead and phosphoric acid serves as a suitable electrolyte. The article holder (not specifically shown in the drawing) should be made of some inert metal (for example, tungsten) or some inert material (for example, graphite) in order that the holder is not etched away by continuous use.

The cathode 27 is connected through a resistor 28 to the negative output terminal 29 of bridge rectifier 22. The metal article or anode 26 to be processed is connected to the movable contact 32 of a relay 33. Contact 32 normally engages or makes with a fixed relay contact 35 which in turn is connected to one terminal of a relay 36, whose other terminal is connected through an adjustable resistor or potentiometer 38 to the positive output terminal 39 of rectifier 22. A filter capacitor 41 is coupled between terminal 39 and cathode 27. Resistor 28 and capacitor 41 .serve to filter the direct current supplied by bridge rectimovable contact 43 of a relay 45. Contact 43 normally engages a fixed contact 46 which in turn is connected through the series arrangement of a unidirectional device or diode 47 and a resistor 48 to a fixed contact 49 of relay 36. Contact 49 normally engages a movable contact 51 which in turn is connected to one terminal of an energy storage device, in the form of a capacitor 52, whose other terminal is grounded. A normally-open fixed contact 54 of relay 36 is connected to one terminal of a relay 55, the other terminal of which is grounded. A movable contact 57, controlled by relay 55, is connected to fixed contact 13 of switch 12. A normally-open fixed contact 58 of relay 55 is connected to one terminal of relay 33 and to one terminal of relay 45, the other terminals of the relays being grounded.

The ungrounded terminal of relay 45 is also connected to a fixed contact 61 of a relay 62. A movable contact 63, controlled by relay 62, normally engages contact 61 and is connected to a fixed normally-open contact 64 of relay 45. A movable contact 65 of relay 45 is connected to fixed contact 13 of switch 12, and a normally-open contact 66 of the relay 45 is connected to one terminal of the primary winding of an auto-transformer 70, the other terminal of the primary being connected to ground. A variable tap 71 of transformer 70 is connected to one terminal of the primary winding 72 of a two-winding transformer 73, the other terminal of primary 72 being grounded. In this way, the winding portion of auto-transformer 70 between tap 71 and ground provides the secon dary winding for the auto-transformer. The secondary winding 76 of transformer 73 is coupled to a conventional full-wave bridge rectifier 77. Transformers 70 and 73 along with rectifier 77 convert the 120-volts A.C. line voltage to direct voltage in order to provide a source of direct current. The direct current supplied by rectifier 77, however, it is substantially greater in magnitude than that supplied by rectifier 22. The negative output terminal 79 of rectifier 77 is connected to the cathode electrode 27, while the positive output terminal 81 is connected to a normally-open fixed contact 82 of relay 33 Secondary winding 84 of transformer 18 is provided with a center tap which is grounded. One terminal of winding 84 is coupled through the series arrangement of a resistor 85 and a diode rectifier 86 to a circuit junction 87. The other terminal of winding 84 is likewise connected through a series resistor 88 and a series diode 89 to junction 87. A capacitor 91 is coupled between junction 87 and ground. Junction 87 is also connected through a pair of series-connected resistors 92, 93 to another circuit junction 94. The junction between resistors 92 and 93 is coupled to ground via a capacitor 95, and junction 94 is coupled to ground through a capacitor 96. Junction 94 is connected through a resistor 97 to a circuit junction 99 which is connected to one terminal of a glow discharge voltage regulator tube 98, whose other terminal is grounded. Transformer 18 and circuit components 85-99 provide a full wave rectifier power supply for converting the 120 volts A.C. line voltage to direct voltage. This power supply provides at junctions 94 and 99 B+ voltages of two different magnitudes. These direct voltages will be well filtered due to the presence of resistors 92 and 93 and capacitors 91, 95 and 96. Regulator tube 98 insures that the magnitudes of the B+ voltages will not vary in response to line voltage variations.

The B+ potentials are employed to operate a conventional free-running, cathode-coupled multivibrator 101 and an amplifying stage 102. More specifically, the multivibrator comprises a pair of triodes encompassed in a single dual triode vacuum tube 100. The cathodes 103 and 104 of the two triodes are joined together and then connected through a cathode resistor 105 to ground. The anode or plate 106 of the left triode is connected through a resistor 107 to a circuit junction 108, while the plate 109 of the right triode is coupled through a resistor 110 to junction 108. A capacitor 112 is coupled between junction 108 and ground and a resistor 113 connects the junction to junction or output terminal 99 of the B+ supply so that B+ operating potential may be applied to multivibrator 101.

The control grid 115 of the right triode is grounded While the control grid 116 of the left triode is connected to ground through a resistor 117. A clamping diode 118 shunts resistor 117 and is polarized such that control grid 116 is prevented from rising above ground potential in order to stabilize the operation of the multivibrator.

The right anode 109 is also coupled via a capacitor 121 to a movable contact 122, controlled by relay 45. Contact 122 normally engages or makes with a fixed contact 123 which is grounded. A normally-open contact 124 of relay 45 is directly connected to the left control grid 116.

The left anode 106 is also coupled via a capacitor 125 to the control grid 126 of a tetrode 127 included in amplifying stage 102. Grid 126 is also connected to ground through resistor 128 which is shunted by a capacitor 129. The screen grid 131 of the tetrode is connected to junction 94 of the B+ power supply by way of a series-connected resistor 132. Cathode 133 of tetrode 127 is grounded through an unbypassed cathode resistor 134. The anode or plate 135 of the tetrode is connected to one terminal of a relay 136, shunted by a capacitor 137, whose other terminal is connected to junction 94.

Relay 136 has a movable contact 138 which is connected to stationary contact 64 of relay 45, and normally engages a fixed contact 139 which in turn is connected to the movable switch contact 141 of an adjustable timer switch 142. This switch has another movable contact 143 which is mechanically, but not electrically, connected to movable contact 141. For example, contacts 141 and 143 may both be mounted on a single wafer constructed of some suitable insulating material so that positioning of the water will cause concurrent movement of contacts 141 and 143.

Switch 142 has six different positions and twelve different stationary contacts equally spaced over 360. For reasons which will become apparent, the three fixed contacts in each of the four quadrants are numbered 1, 2 and 3 in clockwise order. Contact 141 is provided with a projecting portion which is adapted to electrically engage a single one only of the six fixed contacts in the upper left and lower left quadrants, depending on the position of switch 142. Likewise, contact 143 is provided with a projecting portion adapted to electrically engage a single, selected one of the six stationary contacts in the upper right and lower right quadrants.

In the switch position illustrated in the drawing, contact 141 is electrically connected to the No. 2 fixed contact in the lower left quadrant while contact 143 is electrically connected to the No. 2 contact in the upper right quadrant. Clockwise rotation of switch 142 to the very next position will bring contacts 141 and 143 into engagement with the No. 3 contacts in the lower left and upper right quadrants respectively. Rotation of the switch to the next position causes contacts 141 and 143 to engage the No. 1 contacts in the upper left and lower right quadrants respectively.

Movable contact 143 is grounded and the three fixed contacts in the lower left quadrant are joined together and are then connected to one terminal of relay 62, the other terminal of which is grounded. The three terminals in the upper right quadrant are respectively connected to their similarly numbered contacts in the lower right quadrant. In addition, the two No. 1 fixed contacts in the upper right and lower right quadrants are connected via a resistor 145 to control grid 116 of the left triode of multivibrator 101. Similarly, the two No. 2 contacts in the upper right and lower right quadrants are connected through a resistor 146 to control grid 116.

The three fixed contacts in the upper left quadrant are connected in common and to one terminal of a stepping coil 148, the other terminal being grounded. The stepping coil is adapted to actuate a stepping switch 151, which, in addition to a reset or home position, has four different positions. The stepping switch has a movable wiper 152 which is actuated to and through each of the four positions in response to repeated energization of stepping coil 148. The stepping switch is provided with four fixed contacts Nos. 14. Assuming that stepping switch 151 is initially established in its reference or reset position as illustrated, energization of stepping coil 148 effects actuation of wiper 152 to the first position of the stepping switch in which the wiper electrically engages contact No. 1. Subsequent or a secondenergization of coil 148 causes wiper 152 to move into engagement with contact No. 2 of the stepping switch, while a third and a fourth energization of coil 148 effects stepping of wiper 152 to contact No. 3 and then to contact No. 4.

Wiper 152 is connected to the ungrounded terminal of relay 62 and also to one terminal of a homing coil 154, whose other terminal is grounded. Energization of coil 154 effects homing or reset of switch 151 to its reference position. Contacts 1-4 of stepping switch 151 are respectively connected to a series of four correspondingly numbered fixed contacts of a simple four-position multiplier switch 156. The movable contact 157 of switch 156 is connected to fixed contact 64 of relay 45.

Consideration will now be given to an explanation of the operation of the invention. Initially, the operator adjusts timer switch 142 and multiplier switch 156 to establish the time duration of the direct current to be translated through a metal article and the electrolytic bath, thereby to establish the time intervalor cycle of the electropolishing action. As will be seen, the described embodiment is capable of effecting electropolishing for a time interval that may be selectively established at either one-second or multiples thereof up to twelve secondsQIn other words, the electropolishing process may be made to endure for either one second, two seconds,

three seconds, four seconds, etc., up to twelve seconds.

The desired time duration is set up by the conjoint positions of switches 142 and 156. As will be appreciated, the numbers 1, 2 and 3 which designate the stationary contacts of switch 142 indicate 1, 2 and 3 seconds respectively, and the numbers 1-4 designating the fixed contacts of switch 156 indicate the amount by which the seconds established by switch 142 are to be multiplied to provide the desired interval of electropolishing action.

When switch 142 is adjusted to any one of its three positions in which movable contact 141 engages one of the three fixed contacts in the lower left quadrant, while at the same time contact 143 engages the correspondingly numbered fixed contact in the upper right quadrant, switch 156 is ineffective and thus its setting at the time is of no concern. When switch 142 is so positioned, the time duration for the electropolishing direct current will be 1, 2 or 3 seconds, depending on which of the contacts in the lower left and upper right quadrants are connected to movable contacts 141 and 143. As shown in the drawing, timer switch 142 has been set up to establish electropolishing for a two-second interval.

When switch 142 is positioned so that contacts 141 and 143 engage fixed contacts in the upper left and lower right quadrants, the setting of switch 142 must be multiplied by the setting of switch 156. For example, if contacts 141 and 143 are positioned so that they respectively engage the No. 3 contacts in the upper left and lower right quadrants and if multiplier switch 156 is positioned as illustrated, the total time interval for the electropolishing direct current will be 3 X2 or 6 seconds.

It will be assumed in describing the operation of the control circuit that the operator desires to subject a metal article to electropolishing for a time interval of two seconds in duration. Consequently, the operator will adjust switch 142 to the position shown. The position or setting of switch 156 is immaterial since that switch 6 plays no role in the operation of the illustrated circuit for the assumed position of switch 142.

With switch 142 positioned as shown, contact 143 connects the lower terminal of resistor 146 to ground and thus functionally includes that resistor into multivibrator 101. Resistor 146, along with other components of the multivibrator, have a time constant which will insure that once the multivibrator is triggered into operation, in a manner to be explained, an output pulse will be developed by the multivibrator of two seconds in duration. Of course, if switch 142 is positioned so that contact 143 engages the No. 1 contact in the upper right quadrant, resistor 145 will be included in multivibrator 101 and that resistor will have a value which will render the multivibrator capable of producing an output pulse of X one second in duration. With switch 142 adjusted so that contact 143 engages the No. 3 contact in the upper right quadrant, neither of resistors 146 and 145 is effective but the other resistive and capacitive components in the multivibrator have parameters such that the multivibrator is capable of producing an output pulse of three seconds in duration.

In addition to setting up the switching apparatus 142, 156 for establishing the time duration for the electropolishing action, the operator must also turn switch 12 to its ON position in which contacts 11 and 13 engage. A.C. line voltage of 120 volts is therefore impressed across primary windings 15 and 17. The B+ power supply operates in conventional fashion from the voltage of different magnitudes at junctions 94 and 99. The direct voltage at junction 99 is applied through resistors 113, 107 and 110 to plates 106 and 109 of the two triodes in multivibrator 101. Assuming that the filament (not shown) of tube 100 is supplied with appropriate filament voltage, the application of B+ voltabe to plates 106 and 109 will render the multivibrator operable.

However, the cross-coupling circuit from anode 109 to grid 116 is interrupted by normally-open contacts 122 and 124 of relay 45 and thus the multivibrator will not be permitted to initiate free running operation in which it switches back and forth between its two operating conditions, in one condition the left triode being turned on or conducts while the right triode is turned off and in the other condition the left triode is off while the right triode conducts. Grounding of the lower terminal of capacitor 121 through contacts 122 and 123 of relay 45 establishes multivibrator 101 in a predetermined one of its two conditions. In this way, the multivibrator will always be established in the same reference operating condition prior to each electropolishing cycle. Preconditioning of the multivibrator insures that the duration of the direct current, effecting electropolishing, will be precisely timed.

Closing of switch 12 also results in charging of energy storage device 52. Specifically, capacitor 52 is charged by power supply 10 over the following circuit: contacts 11 and 13 of switch 12, contacts 43 and 46 of relay 45, diode 47, resistor 48, and contact 49 and 51 of relay 36. For reasons to become apparent, in the illustrated embodiment resistor 48 is of a value to provide a charging time constant for capacitor 52 of somewhere between .2 and .75 second.

The control circuit is now conditioned or in readiness to effect electropolishing. The operator may now immerse or dip the metal article to be processed into electrolytic bath 25, the article thereupon constituting anode 26. Immersing of metal article 26 completes a normally-incomplete series sensing circuit. More particularly, transformer 16 and bridge rectifier 22 provide a source of direct current. In response to immersing of metal article 26 in the electrolytic bath, current source 16, 22 translates direct current from positive output terminal 39 of the current source through potentiometer 38, relay 36, contacts 35 and 32, metal article or anode 26, electrolytic bath 25, cathode 27, and resistor 28 to negative output terminal 29 of bridge rectifier 22.

This direct current may be called sensing current since the presence thereof effectively indicates that a metal article has been dipped into the electrolytic bath. In the absence of the article the series sensing circuit is not completed. The parameters of transformer 16, rectifier 22, resistor 28 and potentiometer 38 are arranged so that the magnitude of the sensing current will be relatively small (preferably around 2 milliamperes or less) and therefore insufficient to elfect electrolytic metal processing. Resistor 38 is made variable in order that the sensitivity may b precisely adjusted.

The sensing current will, however, be of sufficient amplitude to energize relay 36 which in turn actuates movable contact 51 to bring it into electrical engagement with contact 54. Capacitor 52, which had previously accumulated or stored a charge, is now permitted to rapidly discharge through contacts 51 and 54 and relay 55 to momentarily energize relay 55 and close contacts 57 and 58. The line voltage from source is therefore momentarily impressed across both relays 33 and 45 by way of contacts 11, 13, 57 and 58. Energization of relay 45 opens the connections between contacts 43 and 46 and between 122 and 123 and instead establishes electrical connections between contacts 43 and 64, between 65 and 66, and between 122 and 124. Closing of contacts 43 and 64 completes a latching or holding circuit for both relays 45 and 33 via contacts 11, 13, 43, 64, 63 and 61 so that source 10 is coupled to those relays to maintain them energized after capacitor 52 completes its discharge and relay 55 de-energizes. Making of contacts 65 and 66 completes a circuit between line voltage source 10 and the primary winding of auto-transformer 70. Current source 70, 73, and 77 is therefore rendered capable of delivering a relatively high magnitude of direct current.

Operation of relay 33 results in opening of contacts 32 and 35 and closing of contacts 32 and 82. This opens the sensing circuit, causing relay 36 to de-energize, and effectively substitutes current source 70, 73 and 77, for current source 16, 32. Direct current of a relatively high magnitude and suflicient to effect electrolytic processing or electropolishing of metal article 26 therefore flows from positive output terminal 81 of bridge rectifier 77 and through contacts 82 and 32, anode 26, electrolytic bath 25 and cathode 27 to negative output terminal 79 of rectifier 77. Electrolytic processing continues until relay 45 de-energizes.

Consideration will now be given to the manner in which the time interval between the energization and de-energization of relay 45 is precisely measured in order that electropolishing may be carefully controlled. Opening of contacts 122 and 123 and closing of contacts 122 and 124 by relay 45 completes the cross-coupling circuit from anode 109 and through capacitor 121 to control grid 116 of multivibrator 101. The multivibrator therefore switches from the reference condition in which it was established, and held by the grounding of the lower terminal of capacitor 121, to its other operating condition in which it will remain for a time interval determined by the setting of timer switch 142. Since it has been assumed that the switch is positioned as shown in the drawing, multivibrator 101 will remain in its other condition for two full seconds.

A signal pulse of two full seconds in duration is therefore produced at anode 106 for application to control grid 126 of tetrode 127. The pulse is consequently amplified in the tetrode and is supplied to relay 136 to effect energization thereof. Since multivibrator 101 triggers from one condition to the other in response to energization of relay 45 and completion of its cross-coupling circuitry via capacitor 121, the two-second duration pulse essentially starts at the same time relay 45 is initially energized.

Energization of relay 136 opens contacts 138 and 139. Upon the conclusion of the two-second pulse, relay 136 de-energizes and contact 138 returns to its normal position in which it engages contact 139. This completes a circuit from the high potential or ungrounded terminal of line voltage source 10 to the ungrounded terminal of relay 62. Specifically, AC. power supply 10 is coupled to relay 62 over the following path: contacts 11, 13, 43, 64, 138, 139, 141, the No. 2 contact in the lower left quadrant of switch 142, and then to the ungrounded terminal of relay 62. The relay thereupon energizes and opens contacts 61 and 63 to interrupt the holding or latching circuit for relays 45 and 33. These relays therefore de-energize, thereby opening contacts 65 and 66 and also contacts 32 and 82 to effectively terminate the translation of direct current from bridge rectifier 77 and through metal article 26 and electrolytic bath 25. This in turn terminates electrolytic processing or polishing of the article.

One of the salient features of the invention resides in terminating the electrolytic processing even though metal article 26 remains immersed in bath 25. In fact, the metal article may remain in the bath indefinitely and yet a repeat of the electrolytic processing is prevented. When relay 33 de-energizes, the normally-incomplete series sensing circuit is again completed, and sensing current from bridge rectifier 22 again flows through bath 25 and article 26 to effect energization of relay 36. Energy storage device 52 will therefore again be coupled to relay 55 via contacts 51 and 54. However, at that time capacitor 52 is not in a charged condition so no current will flow through relay 55 to effect operation thereof.

To explain, since contacts 43 and 46 are disengaged by energization of relay 45, the charging circuit for capacitor 52 is open so long as relay 45 operates. As a result, the capacitor never has an opportunity to recharge while electropolishing occurs. At the conclusion of the electropolishing action and when relay 45 deenergizes, contacts 43 and 46 once again make but at essentially the same instant relay 33 de-energizes which causes relay 36 to energize and open contacts 49 and 51. Hence, the charging circuit for capacitor 52 will still be incomplete. Even if there is a slight delay in the operation of the various relays and the charging circuitry is momentarily completed, energy storage device 52 will still not acquire an appreciable charge because of the duration of the charging time constant provided by resistor 48. As mentioned previously, this time constant is preferably in the neighborhood between .2 and .75 second.

As a consequence, retaining of the metal article in the electrolytic bath after the conclusion of the processing cycle will not result in re-energization of relay 55 since capacitor 52 will not have acquired a charge and thus no appreciable current flows from capacitor 52 to relay 55.

Removing of article 26 from the electrolytic bath renders the sensing circuit incomplete and this causes relay 36 to deenergize. Energy storage device 52 is therefore once again coupled through contacts 51 and 49, resistor 48, diode 47, and contacts 46, 43, 13 and 11 to the high potential terminal of line voltage source 10. Capacitor 52 thus once again charges and conditions itself so that it may initiate another electrolytic processing cycle. A subsequent immersing of either the same metal article or a completely different metal article in the electrolytic bath results in the same sequence of operations as discussed previously. Electropolishing takes place for the precise desired time interval. Such processing occurs merely by the operator removing the first metal article and then subsequently reimmersing it or immersing another article in the bath. Note that no adjustments, positions or manipulations of controls must be made by the operator.

The charge condition of capacitor 52 consequently determines whether electropolishing current from bridge 77 will be permitted to flow through the electrolytic bath and the metal article to effect electrolytic processing of the article. The control circuit of the invention effectively includes current supplying means having a plurality of operating conditions, a predetermined one of which renders the current supplying means capable of supplying direct current. Specifically relays 33 and 45 must be energized to effect current flow from bridge 77 to. the electro- 9 lytic cell. Capacitor 52 may be considered conditioning means operable before the metal article is immersed in the bath for establishing the current supplying means in that predetermined condition, the current supplying means being operable responsive conjointly to being established in its predetermined one condition and to immersing of the metal article in the bath for translating direct current through the metal article and the bath to effect electropolishing. The automatic timing apparatus provides means for automatically terminating the direct current upon the expiration of a predetermined time interval, thereby to terminate the electrolytic processing even though the article remains immersed in the bath. Contacts 49 and 51 efiectively provide means for preventing the establishment of the current supplying means in its predetermined one condition, thereby to prevent a repeat operation of the current supplying means, until the article has been removed from the bath.

When it is desired to subject a metal article to electrolytic processing for more than a three-second time duration, timer switch 142 is positioned to utilize the contacts in the upper left and lower right quadrants, while at the same time multiplier switch 156 is appropriately positioned. As an example, assume that it is desired to effect electropolishing for six full seconds. The operator therefore adjusts switch 142 so that contacts 141 and 143 connect respectively with the No. 3 contacts in the upper left and lower right quadrants. Switch 156 is set to the position illustrated in the drawing. The metal article is then dipped in bath 25 and, in the manner discussed hereinbefore, relay 45 energizes to effect the translation of direct current through bath 25 and article 26 to realize electropolishing.

Also in response to energization of relay 45, multivibrator 101 produces a pulse of three seconds in duration which in turn is amplified in amplifier 102 and supplied to relay 136 to efiect operation thereof. As a result, three seconds after relay 45 energizes, relay 136 de-energizes to complete a circuit from the high potential terminal of line voltage source 10 to stepping coil 148. More particularly, the circuit is completed over the following path: contacts 11, 13, 43, 64, 138, 139, 141, No. 3 contact in upper left quadrant, and to the stepping coil. Coil 148 therefore energizes to cause stepping of switch 151 from its reset to its first condition. In so doing, wiper 152 of the stepping switch moves from its reset contact to its No. 1 contact.

Meanwhile, relay 45 remains energized and thus multivibrator 101 is permitted to execute another cycle of operation thereby to produce another three-second duration output pulse. Preferably, the circuit components of the multivibrator are arranged so that the multivibrator, when free running, is established in its operating condition, which produces an output pulse for energizing relay 136, for an interval which is considerably longer than the interval during which the multivibrator is in its other or alternate operating condition. In this way, the time interval between the successive three-second pulses will be extremely small in order that the total time covered by the two pulses will be approximately six seconds.

Upon the conclusion of the second three-second pulse from multivibrator 101, relay 136 de-energizes to again complete a circuit from voltage source 10 to stepping coil 148 to cause stepping of switch 151 from its first to its second .position. However, since switch 156 had been previously positioned by the operator to its second position, at the instant wiper 152 engages the No. 2 contact of switch 151 a circuit is completed from the high potential terminal of line voltage source 10 to the ungrounded terminal of relay 62 and also to the ungrounded terminal of homing coil 154. Specifically, AC, voltage from source 10 is applied to both relay 62 and coil 154 via contacts .11, 13, 43, 64, 157, the No. 2 contacts of switches 156 and 151 and wiper 152. Energization of relay 62 effects de-energization of relays 45 and 33 as discussed previously, which in turn effects the termination of electro- 10 polishing current through the electrolytic cell to complete the electrolytic action. Operation of coil 154 effects homing of stepping switch 151 to its reset or reference position.

If, for example, electrolytic processing for a 12-second interval is desired, switch 156 would be set to its fourth position. In that event, multivibrator 101 would be permitted to operate for four complete cycles in order to produce four 3-second pulses.

Of course, by employing a timer switch with a greater number of positions than that shown and by employing stepping and multiplier switches with many more positions than that shown time intervals of any desired length may be obtained.

While a particular embodiment of the invention has been shown and described, modifications may be'made, and it is intended in the appended claims to cover all such modifications as may fall within the true spirit and scope of the invention.

I claim:

1. A control circuit for controlling electrolytic metal processing of a metal article immersed in an electrolytic bath, comprising:

control means, operable responsive to immersing said metal article in said electrolytic bath, for translating direct current through said metal article and said bath to etfect electrolytic processingof said article; means for automatically terminating said direct current upon the expiration of a predetermined time interval, thereby to terminate said electrolytic processing even through said article remainsimmersed in said bath; and circuit means including the. bath for preventing a repeat operation of said control means until said metal article has been removed from said bath.

2. A control circuit for controlling electrolytic metal processing of a metal article immersed in an electrolytic bath, comprising:

current supplying means having a plurality of operating conditions;

conditioning means operable before said metal article is immersed in said bath for establishing said current supplying means in a predetermined one of its conditions; said current supplying means being operable responsive conjointly to being established in its predetermined one condition and to immersing of said metal article in said bath for translating direct current through said metal article and said bath to effect electrolytic processing of said article; means for automaticall terminating said direct current upon the expiration of a predetermined time interval, thereby to terminate said electrolytic processing even though said article remains immersed in said bath;

and circuit means including the bath for automatically preventing the establishment of said current supplying means in its predetermined one condition, there by to prevent a repeat operation of said current supplying means, until said article has been removed from said bath.

3. A control circuit for controlling electrolytic metal processing of a metal article immersed in an electrolytic bath, comprising:

a device having first and second operating conditions;

conditioning means operable before said metal article is immersed in said bath for initially establishing said device in its first condition;

current supplying means, operable responsive conjointly to establishing said device in its first condition and to immersing of said metal article in said bath, for translating direct current through said article and bath to effect electrolytic processing of said metal article;

means for automatically terminating said direct current upon the expiration of a predetermined time interval,

4 thereby to terminate said electrolytic processing even though said metal article remains immersed in said electrolytic bath;

and circuit means including the bath for preventing the establishment of said device in its first condition, thereby to prevent a repeat operation of said current supplying means, until said article has been removed from said bath, whereupon said conditioning means again establishes said device in its first condition.

4. Electrolytic apparatus including a control circuit for controlling electrolytic metal processing of a metal article immersed in an electrolytic bath, comprising:

an electrical energy storage device;

means for charging said storage device;

sensing means, responsive to immersing said metal article in said electrolytic bath, for discharigng said storage device;

means responsive to the discharge of said device for translating direct current through said electrolytic bath and said metal article for a predetermined time interval to eifect electrolytic processing said metal article, the process automatically terminating upon the conclusion of said predetermined time interval even though said metal article remains immersed in said bath;

and means for preventing charging of said storage device until said article has been removed from said bath.

5. Electrolytic apparatus including a control circuit for controlling electrolytic metal processing of a metal article immersed in an electrolytic bath, comprising:

a capacitor;

means operable before said metal article is immersed in said bath for charging said capacitor;

a normally-incomplete series sensing circuit, including a first source of direct current and said bath, which is completed when said metal article is immersed in said bath, sensing current thereby flowing through said bath and article but of a magnitude insuflicient to effect electrolytic metal processing;

means responsive to said sensing current for discharging said capacitor;

means, including :a second source of direct current, responsive to the discharge of said capacitor for translating direct current through said electrolytic bath and said metal article for a predetermined time interval and of sufiicient magnitude to effect elec- 'trolytic processing of said metal article, the process automatically terminating upon the conclusion of said predetermined time interval even though said metal article remains immersed in said bath;

and means, including said sensing circuit, for preventing charging of said capacitor until said article has been removed from said bath.

6. Electrolytic apparatus including a control circuit for controlling electropolishing of a metal article immersed in an electrolytic bath, comprising:

current supplying means having a plurality of operating conditions;

conditioning means operable before said metal article is immersed in said bath for establishing said current supplying means in a predetermined one of its conditions,

said current supplying means being operable responsive conjointly to being established in its predetermined one condition and to immersing of said metal article in said bath for translating direct current through said metal article and said bath to effect electropolishing of said article;

means for automatically terminating said direct current upon the expiration of a predetermined time interval, thereby to terminate electropolishing even though said article remains immersed in said bath;

and circuit means operative through the bath for preventing the establishment of said current supplying means in its predetermined one condition, thereby to prevent a repeat operation of said current supplying 12 means, until said article has been removed from said bath. 7. Electrolytic apparatus including a control circuit for controlling electrolytic metal processing of a metal article 5 immersed in an electrolytic bath, comprising:

a pulse generator for producing, when actuated, a pulse of a predetermined time duration;

means, operable responsive to immersing said metal article in said electrolytic bath, for actuating said pulse generator to produce a pulse of said predetermined time duration;

means coupled to and controlled by said pulse generator for translating direct current through said metal article and said :bath for said predetermined time duration to effect electrolytic processing of said article;

and means for preventing a repeat actuation of said pulse generator until said metal article has been removed from said bath.

8. Electrolytic apparatus including a control circuit for controlling electrolytic metal processing of a metal article immersed in an electrolytic bath, comprising:

a multivibrator having first and second operating conditions for producing, when actuated from its first condition to its second condition, a pulse of a predetermined time duration;

means for initially establishing said multivibrator in its first condition;

means, operable responsive to immersing said metal article in said electrolytic bath, for actuating said multivibrator from its first to its second condition to produce a pulse of said predetermined time duration;

means coupled to and controlled by said multivibrator for translating direct current through said metal article and said bath for said predetermined time duration to effect electrolytic processing of said metal article;

and means for preventing a repeat actuation of said multivibrator until said metal article has been removed from said bath.

9. Electrolytic apparatus including a control circuit for controlling electrolytic metal processing of a metal article immersed in an electrolytic bath, comprising:

a pulse generator for producing, when actuated, a pulse .of a predetermined time duration;

adjustable means coupled to said generator for changing the duration of said pulse;

means, operable responsive to immersing said metal article in said electrolytic bath, for actuating said pulse generator to produce a pulse of a selected time duration as determined by said adjustable means;

means coupled to and controlled by said pulse generator for translating direct current through said metal article and said bath, during a time interval of said selected duration, to effect electrolytic processing of said article;

and means for preventing a repeat actuation of said pulse generator until said metal article has been removed from said bath.

10. Electrolytic apparatus including a control circuit for controlling electrolytic metal processing of a metal article immersed in an electrolytic bath, comprising:

a pulse generator for producing, when actuated, a pulse of a predetermined time duration to establish a time delay of said same predetermined duration;

time multiplying means coupled to said pulse generator for effectively multiplying the length of said time delay;

means, operable responsive to immersing said metal article in said electrolytic bath, for actuating said pulse generator;

means coupled to and controlled by said pulse generator and said multiplying means for translating direct current through said metal article and said bath, for a time interval of a duration greater than said 13 14 predetermined duration of said time delay, to effect 2,564,823 8/1951 Wallace 204-228 electrolytic processing of said article; FOREIGN PATENTS and means for preventing a repeat actuation of said pulse generator until said metal article has been re- 580,100 8/1946 Great Britain moved from said bath. 5

References Cited JOHN H. MACK, Przmarl'y Exammer: UNITED STATES PATENTS D. R. VALENTINE, Asszstant Examiner.

2,494,121 1/1950 Grainger 204-228 X 

1. A CONTROL CIRCUIT FOR CONTROLLING ELECTROLYTIC METAL PROCESSING OF A METAL ARTICLE IMMERSED IN AN ELECTROLYTIC BATH, COMPRISING: CONTROL MEANS, OPERABLE RESPONSIVE TO IMMERSING SAID METAL ARTICLE IN SAID ELECTROLYTIC BATH, FOR TRANSLATING DIRECT CURRENT THROUGH SAID METAL ARTICLE AND SAID BATH TO EFFECT ELECTROLYTIC PROCESSING OF SAID ARTICLE; MEANS FOR AUTOMATICALLY TERMINATING SAID DIRECT CURRENT UPON THE EXPIRATION OF A PREDETERMINED TIME INTERVAL, THEREBY TO TERMINATE SAID ELECTROLYTIC PROCESSING EVEN THROUGH SAID ARTICLE REMAINS IMMERSED IN SAID BATH; AND CIRCUIT MEANS INCLUDING THE BATH FOR PREVENTING A REPEAT OPERATION OF SAID CONTROL MEANS UNTIL SAID METAL ARTICLE HAS BEEN REMOVED FROM SAID BATH. 